The present invention relates to a carrier tape system used for packaging, transporting, and automatically taking out components that are placed in the pockets of a carrier tape. More particularly, the present invention is directed to apparatus and methods for uniformly sealing and peeling a cover tape that is used to protect the components placed in the pockets of the carrier tape. Furthermore, the present invention provides apparatus and methods for minimizing or eliminating surface irregularities and distortions on bonding zones of the carrier tape.
Electronic components such as semiconductor chips, devices, integrated circuits, and the like are generally developed and manufactured by one manufacturer and transported to another manufacturer or customer for further processing. For example, after manufacturing semiconductor chips in a fabrication or xe2x80x9cclean roomxe2x80x9d facility, the chips are generally packaged and transported to another manufacturer or customer, for example, a computer wholesaler, so that the wholesaler can mount them to printed circuit boards or the like.
When components are packaged and transported from one manufacturer to another, it is critical that the components be packaged and transported with minimal damage. By their very nature, small electronic components (e.g., semiconductor chips, devices, and integrated circuits) are light objects and susceptible to damage. Thus, it is important that these components be packaged and transported in a manner that minimizes/eliminates damage to them.
Currently, the semiconductor fabrication industry implements a JEDEC standard carrier tape system to package and transport semiconductor components. Conventional carrier tape systems allow the component manufacturers to package and transport the components to their customers with minimal damage while allowing the customers to efficiently unload the components using an automated pick and place machine.
FIGS. 1A-1C illustrate various views of a conventional carrier tape system. For example, FIG. 1A illustrates a perspective view, FIG. 1B illustrates a top view, and FIG. 1C illustrates a cutaway end view of a section taken along line Axe2x80x94A of the conventional carrier tape system. Reference will be made to FIGS. 1A-1C concurrently for a more complete understanding of the conventional system.
A conventional carrier tape 2 includes multiple thermoformed pockets 4 formed along its longitudinal direction for storing individual components 6. The carrier tape 2 also includes a row of advancement holes 8 formed longitudinally along one side of the carrier tape 2. The advancement holes 8 are used for locating and feeding the components 6 into the automated pick and place machine (not shown).
In conventional carrier tape systems, surface irregularities and distortions are typically formed on the top surface of the carrier tape 2. These surface irregularities and distortions have a significant influence on the uniformity of the bonding strength between the carrier tape 2 and the cover tape 10. Surface irregularities and distortions are generally formed on the carrier tape 2 as a result of thermoforming the pockets 4 or from subsequent handling of the carrier tape 2. Such surface irregularities and distortions may be in a form of small bumps 14 or grooves 16, which propagate out from or between the pockets 4.
During the packaging process, the components 6 are loaded into the pockets 4 of the carrier tape 2. After the components 6 are successfully loaded into the pockets 4, a cover tape 10 is applied over the pockets 4 using, for example, a sealing iron (not shown) to secure the components 6 contained therein. The cover tape 10 protects and retains the components 6 in the pockets 4 of the carrier tape 2. In general, the cover tape 10 is heat bonded over the carrier tape 2 along a pair of bonding portions 12. In other words, only the outer portions (corresponding to bonding portions 12) of the cover tape 10 are heat bonded to the carrier tape 2 along the longitudinal direction.
After sealing the pockets 4 of the carrier tape 2 with the cover tape 10, the components 6 are transported to another manufacturer/customer. After receiving the carrier tape 2, it is fed into the pick and place machine along its longitudinal direction using advancement holes 8. The cover tape 10 is simultaneously peeled/removed from the carrier tape 2. Thereafter, the components 6 in the pockets 4 of the carrier tape 2 are taken out and mounted to printed circuit boards or the like.
An important consideration using the heat bonding process as described above is that the cover tape 10 must be peeled back from the carrier tape 2 with a uniform amount of force before the components 6 are taken out of the pockets 4. In other words, while separating the cover tape 10 from the carrier tape 2, the force required for such separation should be constant with respect to the longitudinal direction of the carrier tape 2. However, because of surface irregularities and distortions, the required separation force may not be constant. For example, a greater force may be required to separate the cover tape 10 from the carrier tape 4 where there are xe2x80x9chigh spotsxe2x80x9d (i.e., bump 14 of FIG. 1C) and a smaller force may be required in regions where there are lower spots. As a result, the force needed to separate/peel the cover tape 10 from the carrier tape 2 may not be uniform from one region to another. Undulations may result in the carrier tape 2 as the cover tape 10 is separated/peeled. Such undulations may undesirably separate the components 6 from the pockets 4 of the carrier tape 2 or change the placement of the components 6, thereby leading to obstructions in using the automated pick and place machine.
Small surface irregularities and distortions as described above can cause differences in contact pressure during the heat bonding process. As the cover tape 10 is sealed to the carrier tape 2 on the bonding portions 12, xe2x80x9chigh spotsxe2x80x9d will tend to bond better than lower spots, thereby causing variations in the bonding strength. Achieving uniform release tension is often very difficult when such variations in the bonding strength exists and continues to be a major problem in the carrier tape industry.
FIG. 2A illustrates a top view and FIG. 2B illustrates an exploded top view of a section of another conventional carrier tape. Similar to the carrier tape 2 of FIGS. 1A-1C, the carrier tape 22 includes multiple thermoformed pockets 24 for storing components and advancements holes 28 for the automated pick and place machine. As shown in more detail, surface distortions 26 are formed on the carrier tape 22 from thermoforming the pockets 24 and/or subsequent handling the carrier tape 22. Such distortions 26 propagate to the heat bonding portions, thereby requiring variations in the force needed to remove the cover tape from the carrier tape 22.
The carrier tape is made generally made from, but not limited to, thermoplastic resin, polystyrene or ABS (acrylonitrile butadiene-styrene) with or without additives, and the cover tape is made from, but not limited to, polyester, polypropylene or polyethylene having heat sensitive adhesives with or without additives.
U.S. Pat. No. 4,736,841 (""841 patent) also discloses various examples of other prior art carrier tape systems. One particular embodiment in the ""841 patent includes a carrier tape that has a pair of step portions extending longitudinally along opposite sides of the carrier tape. The raised portions of the carrier tape are used as bonding portions to heat bond the cover tape thereto, where the step portions are also used as boundaries for applying the cover tape. Consequently, a recessed center portion is prevented from making contact with the cover tape as the step portions are used as physical boundaries. Thus, in this particular prior art embodiment, the boundaries of each of the bonding portions are defined by the step portions, which extend longitudinally along the carrier tape. In addition, the ""841 patent does not address the problem of minimizing/eliminating surface irregularities and distortions in the bonding portions/zones of the carrier tape.
It is an object of the present invention to provide apparatus and methods for improving adhesion between a carrier tape and a cover tape.
It is another object of the present invention to provide apparatus and methods for providing a more uniform sealing and peeling process between a cover tape and a carrier tape.
It is a further object of the present invention to provide apparatus and methods for minimizing/eliminating surface irregularities and distortions from the bonding portions/zones of a carrier tape.
It is yet another object of the present invention to provide apparatus and methods for improving cover tape bond strength uniformity.
It is another object of the present invention to provide a carrier tape having surface transitions along each longitudinal side to minimize/eliminate surface irregularities and distortions on the bonding portions/zones of the carrier tape.
The present invention relates to apparatus and methods for sealing and peeling a cover tape from a carrier tape in a uniform manner. The carrier tapes of the present invention include surface transitions that minimizes/eliminates the presence of surface irregularities and distortions on the carrier tape such that the cover tape can be uniformly applied and removed to/from the carrier tape. These surface transitions are used to improve bond strength uniformity between the cover tape and the carrier tape.
Apparatus and methods for minimizing/eliminating the presence of surface irregularities and distortions in bonding zones of the carrier tape is achieved by adding surface transitions along each longitudinal side of the carrier tape. This can be accomplished by adding a pair of continuous ribs or step portions between the pockets and the heat bonding zones. In other embodiments, there can be more, than two surface transitions on the carrier tape (i.e., four continuous ribs, two continuous ribs on each side of the carrier tape extending longitudinally). The surface transitions act as physical barriers to prevent propagation of surface irregularities and distortions from the thermoformed pocket area to the heat bonding zones. In addition, the surface transitions also act as stiffening members to help keep the heat bonding zones as flat as possible during subsequent handling of the carrier tape.